Hello all!

I've been researching the differences between the early model W126 CCU and the later units. I've noticed that mine (a 1985) is quite different from the later models.

For example, mine has two 12 pin connectors (one for left and right) and the later style ones have two 14 pin connectors. The later ones have built in backlighting, where as mine does not. Wheel location is slightly different between the two as well.

I need more help though. Specifically, can someone provide pinouts for each of these units? What is the technical difference between the 12pin and 14pin connector?

Reason I'm asking is to use a later CCU (14 pin connectors) in an early car (12 pin connectors). I'm replacing the wood trim in my car, and I have wood pieces from a later car with the wheel in a slightly different location. Meaning I have to use the later CCU to fit.

PS: My theory is that the extra two connectors are for the built in backlighting. However, I'd like concrete evidence. All help is appreciated.

Resolved!

See below link from another message board. Looks like this is a damn near impossible swap.

Climate control interchangeability - Page 3 - Mercedes-Benz Forum

Any other input is welcome.

The unit in my '83 SD illuminates. There are a couple of bulbs covered by tape to light the buttons. I don't remember how to get to the bulbs for the thumbwheels.

The controllers are different because the systems are different. Early systems have an external temperature controller and discreet blower settings. Later systems have integrated temperature control, seemingly continuous blower settings and a user selectable recirculate feature. The latter probably accounts for the increased pin count.

Have you tried moving early innards to a later housing or grafting a later face to your early housing?

Sixto
83 300SD
98 E320 wagon

What I'm basically going to have to do is search for a Zebrano wood face plate for an early CCU. Which is hard to do online without having the part in person. The wheel location is ever so slightly off to the left on the later ones, and its hard to catch it in photos.

That being said, I was able to graft my early power window switches onto a late Zebrano wood center console face plate. That was easy since I only need to enlarge the holes with a dremel (Okay I make it sound easy, truth be told it took a very steady hand, and its still not perfect).

The CCU face plate is whole different ball game unfortunately.

Maybe I wasn't clear - can you put what's inside your early ACC controller into a later style ACC control case which fits the later style wood panel? Maybe you can modify the early case so the thumbwheels line up with later wood panel.

Sixto
83 300SD
98 E320 wagon